PHD will now handle media for Warner Brothers Home Entertainment and its new interactive division, in addition to the theatrical business it previously held.
Its sister Omnicom agency, Manning Gottlieb OMD, previously handled the £4 million home-entertainment business, covering advertising for Warner's DVD releases, but was unable to pitch for the combined business owing to conflict with Sony Pictures.
The consolidation builds on a long relationship between Warner and PHD, which has handled the film releases business since 1999.
Danni Murray, the media controller for Warner Brothers Entertainment UK, said: "We are confident PHD has shown the innovative media thinking to help us deliver successful media communications across a broader canvas."
Warner film releases supported last year by significant media spend included 300, Ocean's 13 and Harry Potter and the Order of the Phoenix.
Separately, Warner Music is close to concluding a pitch for its £4 million business.